The prior art has disclosed many different types of bags. A simple bag is a pillow-style with no gussets, either on the sides or at the ends. A further style is one which is side-gusseted and sealed all the way across the ends, called a "pinch-bottom bag," and because of the side gussets, this bag stacks better when laid flat, so that the bags may be stacked, for example, on a pallet for shipping of a group of bags. This bag is shown, for example, in U.S. Pat. No. 3,468,470.
A further style of bag is a square-ended bag which may stand upright, for example, the ordinary grocery bag made of kraft paper. Where this bag is made from plastic film, as a shipping bag, this square-ended bag stacks even better than the pinch-bottom bag when laid flat and stacked on a pallet. Therefore, such bags may be stacked higher on the pallet for shipping. U.S. Pat. No. 3,973,045 shows, in FIG. 5, a pinch-bottom bag with side gussets wherein the bottom has been sealed all the way across, and shows in FIG. 1 a side-gusseted bag wherein only two thicknesses have been sealed everywhere at the bottom, including a central portion and the gusset portions. U.S. Pat. No. 3,961,743 discloses a type of bag which is essentially a square-ended bag, but which has longitudinally extending ears which may be tied together to form a grasping handle.
The side-gusseted, pinch-bottom bag, because it has a bottom seal which extends completely across the width of the bag, is unsuitable for a simple machine for filling the bag. If the bag comes in a chain, such as a zig-zag fold of a series of bags or a roll of a series of bags, then any gripper mechanism to grip the side-gusseted bag would grip the side gussets closed, and hence the bag would be difficult to open and also most difficult to fill completely because the gussets are held closed. If the gripper mechanism were somehow constructed to grip only the gussets along the rear panel, for example, then the bag could open almost completely, but somehow the grippers would have to articulate laterally in and out of the gussets in order to get past the completely sealed-across bottom seal.